The present invention is related to electric actuators, and in particular to a controller for electric actuators.
Actuators are employed in a variety of applications to automate the opening and closing of valves. Electric actuators rely on a motor that converts electric energy to mechanical energy to open/close the actuator. For example, permanent magnet motors are oftentimes employed in linear and rotary actuators in applications such as fuel valve actuators. A controller receives an input representing a desired position of the actuator, and generates control signals to regulate the operation of the motor and therefore achieve the desired result.
For example, in one prior art method the controller may make use of a position loop, a speed loop, and a torque loop to control the operation of the electric actuator. The position loop monitors the difference between the desired position and the monitored position, and generates in response a speed command that is provided to the speed loop. In response, the speed loop generates a torque command that is provided to the torque loop that generates command instructions used to control the operation of the electric actuator. However, these control systems do not account for large load parameter variations such as those created by mechanical aspects of the electric actuator, such as those caused by spring-assist closing of the valve associated with the electric actuator.